In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the ostium of the desired coronary artery. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. An over the wire (OTW) balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The OTW catheter has a guide wire lumen which is as long as the catheter. Another type of catheter, a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter may be used. Alternatively, a fixed wire balloon may be used. This device features a guide wire which is affixed to the catheter and cannot be removed.
To help prevent arterial closure, repair dissection, or prevent or lower restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside the artery at the lesion. In particular, a stent is a prosthesis which is generally tubular and which is expanded radially in a vessel or lumen to maintain its patency. Stents are widely used in body vessels, body canals, ducts or other body lumens. The stent may either be a balloon or otherwise mechanically expandable stent or a self-expanding stent.
For the former type, the stent is often delivered on a balloon and the balloon is used to expand the stent exerting radial force on the constricted portion of the body lumen to re-establish patency. A common material for balloon expandable stents is stainless steel.
For the latter type, the self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics. Self-expanding stents are typically constrained onto the delivery catheter by means of a retractable sheath covering the stent. The self-expanding stent expands from a compressed delivery position to its original diameter when released from the delivery device, exerting radial force on the constricted portion of the body lumen to re-establish patency. One common self-expanding stent is manufactured of Nitinol, a nickel-titanium shape memory alloy, which can be formed and annealed, deformed at a low temperature, and recalled to its original shape with heating, such as when deployed at body temperature in the body.
To date, several different types of catheters with retractable sheaths have been disclosed. In one type of catheter, the sheath retracts in a proximal direction. Examples of such catheters are disclosed in WO 98/12988 as well as in U.S. Pat. No. 5,534,007 to St. Germain, both of which are incorporated herein in their entirety by reference. In another type of catheter, as described in U.S. Pat. No. 5,158,548 to Lau and U.S. Pat. No. 5,242,399 to Lau, the sheath is attached to a guidewire and moved in a distal direction to release a stent for delivery. As such, the guidewire cannot be operated independently of the sheath.
The present invention is directed to a catheter having a sheath which is retractable in the distal direction and which is suitable for use as a rapid exchange catheter, an over-the-wire catheter or a fixed wire catheter.